To enhance the removal of model naphthenic acids (NA) from synthetic wastewater and removal of organics in oil sands process-affected water (OSPW) by adsorption, surfaces of commercial charcoal derived activated carbon (AC) and proprietary petroleum coke-derived activated carbon (PAC) were modified. Two different amination processes including a single stage treatment with ammonia gas at an elevated temperature and a two-step treatment of nitration followed by reduction were adopted. All adsorbents showed excellent capacity for the model NAs and OSPW at low pH (<= 4.0). Ammonia treatment was more effective on improvement of adsorption capacity than the nitration followed by reduction method. The effect was more significant for commercial activated carbon compared to PAC, especially for multi-component adsorption at pH 8.0. The kinetics of adsorption improved significantly by the surface modification methods indicating great potential for these adsorbents in continuous column operation. (C) 2016 Elsevier B.V. All rights reserved.